In the broadest sense, the study aims to investigate the impact of specific forms of maternal psychological functioning on mother-infant relations in the first 24 months of life, and to trace the implications of such relations for infant social, emotional, and cognitive development. In particular, the study seeks to identify processes underlying the intergenerational transmission of attachment security and to identify factors related to discontinuity in developmental trajectories. To this end, the project adopts a quasi-experimental design in a prospective study of mothers and their infants. Two groups of primiparous women will be recruited from the antenatal clinic at King College Hospital, London and followed for two years after the birth of their child. The first group will be composed of 20 women meeting the DSM-IV criteria for Borderline Personality Disorder (BPD), a psychiatric condition characterized by disturbed interpersonal relationships. The second group will be composed of 40 women without a psychiatric diagnosis who will be comparable in age, socio-economic status and level of education. The Adult Attachment Interview (AAI) will be employed to assess maternal attachment status. Previous research by the sponsor indicates that women with BPD are most likely to be 'preoccupied' with respect to their attachment status, as assessed by the AAI. Therefore, the composition of the control group will be divided into two sub-groups, reflecting equal distributions of women with 'preoccupied' and 'secure' attachment classifications, as assessed by the AAI. This design will allow an examination of the relative effects of a) BPD in conjunction with maternal 'preoccupied' attachment status, b) 'preoccupied' attachment status when not associated with any psychiatric condition, and c) in relation to maternal 'secure' attachment status and no psychiatric diagnosis. Subjects will participate in multiple assessments across the two year period, including measures of maternal and infant social variables that may affect group differences (i.e., infant temperament, maternal mood and social support); maternal cognitive functioning; observations of mother-infant interactions; and measures of infant socio- emotional and cognitive development. The study has implications for infants at high-risk for developing insecure attachment patterns, deficits in emotional and cognitive development, and impaired parent- child relationships, as well as for future intervention efforts in families at risk for these difficulties.